Glass or plastic substrates are transparent and have a wide variety of uses. However, these substrates are liable to generate static electricity on their surface, because they are insulators. When glass or plastic substrates are used, as they are, as face-plates for displaying devices such as cathode ray tube (CRT), fluorescent indication pipe (FIP), plasma display (PDP), liquid crystal display (LCD), etc., rubbish or dust attaches to the surface of face-plates and the images displayed are difficult to look at. In the case of LCD, moreover, there is sometimes brought about destruction of IC or mistake in display by static electricity generated. In a copy machine 1 equipped with an automatic document feeder (ADF) 2 as shown in FIG. 1, paper clogging is sometimes caused by static electricity generated on a platen glass 3 in the course of feeding documents, whereby continuous feeding of the documents can be made no longer. In the case of plastic substrates, moreover, because of their low surface hardness, the plastic substrates readily receive scuff marks, whereby they sometimes decrease in transparency.
With the view of solving such problems as mentioned above, there are proposed processes for forming on substrates metallic coatings or conductive inorganic oxide coatings by the vapor phase method such as CVD, PVD or sputtering. The coatings obtained by these processes, however, are low in acid resistance as well as in alkali resistance, and liable to scuffing as they are low in resistance to scuffing, though they are excellent in transparency or conductivity. In forming these substrates, it is necessary to use vacuum metallizers and, moreover, there is a limit to an area or shape of the substrate on which the coating can be formed by the vacuum metallizers. Furthermore, in these processes no coatings are formed at low temperatures, and continuous productivity is poor because said processes are carried out batchwise.
In the platen glass coated with such an antistatic coating as mentioned above, the coating formed on the platen glass was sometimes scraped off by the documents fed to ADF or a rubber belt fitted to ADF. When copying is carried out in higher copy sensitivity, that is, at a gray scale, by using a copy machine with such a platen glass as mentioned above, there was brought about such a new problem that the scraped portion are printed as stains on the copy.
There is also proposed a process for imparting conductivity to substrates by coating the substrates with conductive paints prepared by dispersing conductive substances in resin. The coatings obtained by this process, however, had such problems that they are poor in transparency, durability and resistance to scuffing, though they are excellent in conductivity.
The face-plates of displaying devices, on one hand, are required sometimes to have a regular reflection reducing effect (hereinafter called anti-glare) for inhibiting glaring of the face-plates, in addition to the antistatic effect thereof. The following are known as procedures intending to impart anti-glare and antistatic effect to the face-plate of displaying devices. That is, Japanese Patent L-O-P Publn. No. 16452/1986 discloses a process which comprises preheating a face-plate composed of glass or plastics, spraying over said face-plate a colloidal solution of a silicon compound such as a partially hydrolyzed silicic ester or the like, a silicon compound such as silicon tetrachloride or the like, or a solution obtained by mixing said colloidal solution with a water-soluble compound of inorganic metal such as platinum, gold, palladium or tin, and forming a finely uneven coating composed of silicon oxide or its hydrate on the surface of the face-plate, followed by drying and heating.
Further, Japanese Utility Model L-O-P Publn. No. 168951/1984 discloses a process which comprises forming a coating layer on the face-plate by the vacuum deposition or dip method from a mixture of tin oxide or indium oxide and silicon oxide or from a laminate thereof.
In the face-plates obtained by these processes mentioned above, however, anti-glare is insufficient or the antistatic effect thereof varies depending upon the ambient temperature or humidity. Under certain circumstances, moreover, resolving power of the displaying devices equipped with such face-plates sometimes decreased. Furthermore, the coatings formed on the face-plates are poor in adhesion to the face-plates and easily peel off, liable to scuffing because of their low resistance to scuffing, and peel off or flow because of their low durability, whereby anti-glare and the antistatic effect could not be maintained for a long period of time.
By way of Japanese Patent Appln. No. 299686/1986, the present applicant applied for a patent a coating solution for forming a conductive coating, said coating solution being a homogeneous dispersion comprising water and an organic solvent of zirconium oxysalt, silicon alkoxide or its derivative and a conductive substance. The conductive coating obtained by heating a wet coating formed by using the above-mentioned coating solution at a temperature of at least 250.degree. C. is excellent in performance characteristics such as transparency, conductivity and resistance to scuffing. However, the conductive coating obtained likewise but by heating at a temperature below 250.degree. C. is poor in durability, and it was difficult to apply said conductive coating to a plastic substrate. Furthermore, because this coating solution is not always sufficiently stable, the coating solution applied to the substrate came to gel in some cases during the coating operation, particularly a continuous operation by transfer printing, whereby the continuous operation intended met with difficulties. In addition thereto, the coating solution had to be kept at below 15.degree. C. in order to preserve it for an extended period of time.
The present invention is intended to solve such problems associated with the prior art as mentioned above. That is, firstly, an object of the invention is to provide a coating solution (hereinafter called coating solution I) for forming transparent conductive ceramic coatings, said coating solution being a homogeneous solution or dispersion of an acetylacetonate chelate compound and a conductive substance in a mixture of water and an organic solvent.
Secondly, an object of the invention is to provide a coating solution (hereinafter called coating solution II) for forming transparent conductive ceramic coatings, said coating solution being a homogeneous solution or dispersion of an acetylacetonate chelate compound (excluding dialkoxybisacetylacetonatozirconium), a silicon compound and a conductive substance in a mixture of water and an organic solvent.
Thirdly, an object of the invention is to provide a coating solution (hereinafter called coating solution III) for forming transparent conductive ceramic coatings, said coating solution being a homogeneous solution or dispersion of an acetylacetonate chelate compound, alkoxide of metal other than silicon, and a conductive substance in a mixture of water and an organic solvent.
Fourthly, an object of the invention is to provide a coating solution (hereinafter called coating solution IV) for forming transparent conductive ceramic coatings, said coating solution being a homogeneous solution or dispersion of an acetylacetonate chelate compound, a silicon compound, alkoxide of metal other than silicon and a conductive substance in a mixture of water and an organic solvent.
Fifthly, an object of the invention is to provide a substrate (hereinafter called substrate A), such as composed of glass, plastics or the like, on which transparent conductive ceramic coatings being formed by using the coating solution I, II, III or IV, said conductive ceramic coatings being excellent in durability, transparency, resistance to scuffing, adhesion and antistatic effect, and sixthly an object of the invention is to provide a substrate (hereinafter called substrate B) on which transparent conductive ceramic coatings having anti-glare in addition to those performance characteristics as mentioned above, and further to provide processes for preparing such substrates as mentioned above.
Seventhly, an object of the invention is to provide a displaying device (hereinafter called displaying device A) comprising the substrate A as a face-plate.
Eighthly, an object of the invention is to provide a displaying device (hereinafter called displaying device B) comprising the substrate B as a face-plate.
Ninthly, an object of the invention is to provide a copy machine comprising the substrate A as a platen glass.